Cooling structure of a projection tube

ABSTRACT

A cooling structure of a projection tube having a following constitution is disclosed. A chamber in which a liquid coolant for cooling a panel surface is filled is formed on the panel surface of the projection tube and the chamber is defined by the panel surface, a lens which faces the panel surface in an opposed manner and a metal envelope which radiates heat. A first seal member is disposed between the metal envelope and the panel surface, while a second seal member is disposed between the metal envelope and the lens. A holder for pressing the lens in the direction toward the metal envelope is disposed in the periphery of the lens. Pads which have surfaces approximately perpendicular to a tube axis of the projection tube are formed on a funnel portion of the projection tube. A sustainer for supporting the chamber is brought into contact with the pads. The holder and the sustainer are fastened to each other by means of couplers so as to apply pressure to the first seal member and the second seal member whereby the chamber is sealed without coupling the coupler with the metal envelope.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cooling structure of aprojection tube incorporated in a projection TV set, for example.

[0003] 2. Description of the Related Art

[0004] Recently, projection TV sets having a large screen of not lessthan 40 inches have been popularly used. The projection TV set is servedfor projecting an image of a projection tube (PRT) having a screen sizeof approximately 5.5 inches on a screen of approximately 40 inches usingan optical lens, a mirror and the like. In general, a color image isobtained by projecting images from three projection tubes whichrespectively produce monochroic images of red, green and blue on ascreen. In the projection system, for example, to project the image ofapproximately 5.5 inches of the PRT on the screen of 40 inches, theimage is magnified by not less than 50 times in area. Accordingly, theimage of the PRT is required to have an extremely high brightness. Torealize the high brightness, it is necessary to supply a large currentto the small screen of approximately 5.5 inches and this elevates thetemperature of a phosphor screen and a panel glass. The elevation of thetemperature of the phosphor screen gives rise to a problem such as thelowering of light emitting efficiency of a phosphor body or the breakingof the panel glass due to the thermal distortion.

[0005] To solve this problem, it is necessary to cool the phosphorscreen. U.S. Pat. No. 4,731,557 discloses one typical cooling structure.In this cooling structure, to seal a coolant in a chamber, seal membersare provided at two locations and the chamber is sealed by a mechanicalpressure exerted by these seal members. However, this cooling structurestill has several drawbacks including following drawbacks. That is, whena defect exists in the seal member at one location, the liquid leaksfrom the chamber. Further, since it is necessary to mechanically fastenthe seal members using bolts or the like to respectively seal at twolocations, the manufacturing cost is pushed up.

SUMMARY OF THE INVENTION

[0006] Accordingly, it is an object of the present invention to providea cooling structure of a projection tube which can solve such drawbacksand can minimize sealing defects, can reduce the operation cost and themanufacturing cost, and can reproduce parts.

[0007] According to the present invention, in a structure which cools apanel by bringing a liquid into direct contact with a panel surface of aPRT, a chamber which accommodates the liquid is supported on a funnel ofthe PRT. A mechanical pressure necessary for sealing the liquid in thechamber is obtained only by a coupling with a sustaining structure froma funnel.

[0008] With respect to other features of the present invention, in astructure having a chamber which has one side thereof formed of a panelsurface of a PRT, the other side thereof which faces the one side in anopposed manner formed of a lens and a side surface thereof formed of ametal envelope which radiates heat, an adhesive is used as a sealbetween the lens and the metal envelope, and the metal envelope and thesurface of the panel of the PRT are sealed to each other by applying amechanical pressure to a seal member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a cross-sectional view of a liquid cooling structure ofthe present invention.

[0010]FIG. 2 is perspective view of an example of a sustainer.

[0011]FIG. 3 is a perspective view of an example of a holder.

[0012]FIG. 4 is a cross-sectional view of a liquid cooling structure ofanother embodiment of the present invention.

[0013]FIG. 5 is a cross-sectional view of a liquid cooling structure ofstill another embodiment of the present invention.

[0014]FIG. 6 is a conceptual view of a projection TV set.

[0015]FIG. 7 is a cross-sectional view of an essential part of theprojection TV set.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Subsequently, embodiments of the present invention are explainedin reference to attached drawings hereinafter.

[0017]FIG. 1 shows a liquid cooling structure of a first embodiment ofthe present invention. In the drawing, a PRT 1 is comprised of a panel11, a funnel 12 and a neck portion 13 which accommodates an electron gun14.

[0018] While an outer surface of the panel 11 is made flat, an innersurface of the panel 11 is bulged toward an electron gun side thusforming a lens. Pads 15 are formed on a funnel portion. The pads 15 are,in general, formed at four positions of the funnel 12. The pads 15 aremade of glass and are integrally formed with the funnel 12 at the timeof forming the funnel 12 by a press molding. The pads 15 have animportant role. That is, the pads 15 support the whole cooling structurein a manner that the pads 15 are brought into contact with a sustainer2. Surfaces 151 of the pads 15 which are brought into contact with thesustainer 2 are set substantially perpendicular to a tube axis of thePRT 1. In view of the fact that the pads 15 are made of glass, buffersmay be inserted between the pads 15 and the sustainer 2 for preventingthe formation of flaws on the pads 15.

[0019] A liquid coolant 9 is brought into contact with a surface of thepanel 11 of the PRT 1 so as to cool the panel surface. The liquidcoolant 9 is filled in a chamber formed of the panel 11, a lens 5 and ametal envelope 4 for heat radiation. The liquid coolant 9 which isheated by the panel surface is brought into contact with the metalenvelope 4 which is made of material having a good thermal conductivityand heat is radiated from the metal envelope 4. Ethylene glycol or thelike can be used as the liquid coolant 9. The sealing between the metalenvelope 4 and the panel 11 is obtained by a seal member 7, while thesealing between the metal envelope 4 and the lens 5 is obtained by aseal member 8.

[0020] The lens 5 is bulged at a PRT side thereof and is recessed at aside thereof opposite to the PRT side. A hole 41 for filling the liquidcoolant 9 in the chamber is formed in the metal envelope 4. An elasticmember 10 such as a rubber is used as a seal of the hole 41 to cope withthe expansion of the liquid coolant 9 which is brought about by thetemperature elevation. The lens 5 is pressed by a holder 6 and theholder 6 is coupled to the sustainer 2 by couplers 3. In FIG. 1, boltsare used as the couplers 3 and the sealing is obtained by fastening thesustainer 2 and the holder 6 to each other with the use of thesecouplers 3 thus applying pressure to the seal member 7 and the sealmember 8 simultaneously. To ensure the strength and the heat radiationefficiency, the holder 6 may be preferably made of metal. The adjustmentof fastening pressure by the bolts has an important role to ensure thereliability of the sealing of the liquid coolant 9. In this embodiment,the bolts are used as the couplers 3. In this embodiment, since theoperation to apply the mechanical pressure with the use of the bolts isperformed simultaneously on the seal member 7 and the seal member 8, theprobability of the occurrence of defects on seals by an erroneousoperation can be decreased. Further, the operational cost can bereduced.

[0021] In this embodiment, an adhesive may be used exclusively as theseal member 7. With respect to the adhesive, a silicone-based adhesiveis excellent in view of points that the adhesive exhibits the excellentsealing characteristics and enables the reproduction of various parts.Also in this case, the seal member 7 and the seal member 8 receive themechanical pressure for sealing. A lens unit 16 is mounted on the holder6 to magnify an image and to project the magnified image to a screen.

[0022] Although the sustainer 2 shown in FIG. 1 is formed in a plateshape, the sustainer 2 may be formed in a bottomless box shape as shownin FIG. 2. In FIG. 2, numeral 21 indicates an opening which allows thefunnel portion of the PRT 1 to pass therethrough and a surface 22 isbrought into contact with the pads 15 formed on the funnel portion. Lugs23 are provided for being coupled with the holder 6 by means of couplers3. With the use of the sustainer 2 shown in FIG. 2, the length of thecouplers 3 can be shortened.

[0023] Further, although the holder 6 shown in FIG. 1 is formed in aplate shape, by forming the holder 6 in a shape shown in FIG. 3, thelength of the couplers 3 can be shortened. In FIG. 3, an opening 61 isprovided for allowing the image to be projected on the screen to passtherethrough and a flat surface portion 62 brings the periphery of thelens into pressure contact with the metal envelope 4 side. Lugs 63 arecoupled to the sustainer 2 by means of the couplers 3. With the use ofthe holder 6 shown in FIG. 3, the length of the couplers 3 cab beshortened. Further, with the coupled use of the sustainer 2 shown inFIG. 2 and the holder 6 shown in FIG. 3, the length of the couplers 3can be further shortened.

[0024]FIG. 4 shows a liquid cooling structure according to anotherembodiment of the present invention. Parts identical with those shown inFIG. 1 are indicated by same numerals.

[0025] In this embodiment, a seal member 8 is made of an adhesive. Withrespect to the adhesive, a silicone-based adhesive is excellent in viewof points that the adhesive exhibits the excellent sealingcharacteristics and enables the reproduction of various parts.Accordingly, in this embodiment, the holder 6 shown in FIG. 1 isunnecessary. In this embodiment, by fastening a metal envelope 4 and asustainer 2 by means of couplers 3, the sealing between the metalenvelope 4 and a panel 11 is obtained with the use of a seal member 7.Also in this embodiment, bolts are used as the couplers 3. Also in thisembodiment, the fastening of bolts for obtaining the sealing isperformed by a single operational step. Further, the sealing obtained bythe mechanical pressure is performed only one place which corresponds tothe seal member 7. Here, a lens unit 16 is mounted on the metal envelope4.

[0026]FIG. 5 shows a liquid cooling structure of another embodiment inwhich a lens 5 is mounted to the inside of a metal envelope 4 by meansof an adhesive 8. In the structure shown in FIG. 4, when a liquidcoolant 9 is swelled due to the elevation of temperature, the pressureexerted by the liquid acts in the direction to peel off the lens 5 fromthe metal envelope 4, in the structure shown in FIG. 5, the pressureexerted by the liquid acts-in the direction to bring the lens 5 intopressure contact with the metal envelope 4 and hence, it is advantageousto obtain the reliability of the sealing of the lens 5.

[0027] In the embodiments shown in FIG. 4 and FIG. 5, the lens 5 and themetal envelope 4 are preliminarily integrally formed by means of theadhesive and thereafter the metal envelope 4 and the PRT aremechanically coupled to form a chamber for the liquid coolant. Inrespective embodiments shown in FIG. 4 and FIG. 5, the lens unit 16 ismounted on the metal envelope 4.

[0028]FIG. 6 is a conceptual view of a projection TV set. Images from aPRT 1R which forms a red image, a PRT 1G which forms a green image and aPRT 1B which forms a blue image are projected on a screen 17 afterpassing through respective lens units 16. The red image, the green imageand the blue image are converged on the screen 17. FIG. 7 is across-sectional view of an essential portion of the projection TV set.The images from the PRTs 1 pass through the lens units 16 and arereflected on a mirror 18 and are projected on the screen 17.

What is claimed is:
 1. A cooling structure of a projection tubecharacterized in that a chamber in which a liquid coolant for cooling apanel surface is filled is formed on the panel surface of the projectiontube, a liquid coolant is present in the chamber, the chamber is definedby the panel surface, a lens which faces the panel surface in an opposedmanner and a metal envelope which radiates heat, a first seal member isdisposed between the metal envelope and the panel surface, a second sealmember is disposed between the metal envelope and the lens, a holder forpressing the lens in the direction toward the metal envelope is disposedin the periphery of the lens, pads which have surfaces thereof arrangedapproximately perpendicular to a tube axis of the projection tube areformed on a funnel portion of the projection tube, a sustainer forsupporting the chamber is brought into contact with the pads, and theholder and the sustainer are fastened to each other by means of couplersso as to apply pressure to the first seal member and the second sealmember, whereby the chamber is sealed without coupling the couplers withthe metal envelope.
 2. A cooling structure of a projection tubeaccording to claim 1, a surface of the sustainer which is brought intocontact with the pad portion is formed in a plate shape.
 3. A coolingstructure of a projection tube according to claim 1, wherein thesustainer is formed in a bottomless box shape, lugs for coupling thesustainer with the holder are formed on a bottomless side of thesustainer, and the other surface of the sustainer includes an openingwhich allows the funnel portion to pass therethrough and a surface whichis brought into contact with the pads.
 4. A cooling structure of aprojection tube according to claim 1, wherein lugs which are extendedtoward the projection tube side to be coupled with the sustainer areintegrally formed with the holder.
 5. A cooling structure of aprojection tube according to claim 1, wherein buffers are disposedbetween pads and the sustainer.
 6. A cooling structure of a projectiontube according to claim 1, wherein the first seal member is an adhesive.7. A cooling structure of a projection tube characterized in that achamber in which a liquid coolant for cooling a panel surface is filledis formed on the panel surface of the projection tube, a liquid coolantis present in the chamber, the chamber is defined by the panel surface,a lens which faces the panel surface in an opposed manner and a metalenvelope which radiates heat, a first seal member is disposed betweenthe metal envelope and the panel surface, a second seal member isdisposed between the metal envelope and the lens, the second seal memberis formed of an adhesive, pads which have surfaces thereof arrangedapproximately perpendicular to a tube axis of the projection tube areformed on a funnel portion of the projection tube, a sustainer forsupporting the chamber is brought into contact with the pads, and thesustainer and the metal envelope are fastened to each other by means ofcouplers with a mechanical forth so as to apply pressure to the firstseal member, whereby the chamber is sealed.
 8. A cooling structure of aprojection tube according to claim 7, wherein the second seal member isformed outside the metal envelope.
 9. A cooling structure of aprojection tube according to claim 7, wherein the second seal member isformed inside the metal envelope.